You basically build roads, farms and a mine or two. Unless something really terrible happened to Oleg’s trading post or you chose not to claim the castle, you basically need to build a road from there to your castle and then you need to build farms to feed everyone and then you need to build mines or sawmills to start growing the economy.

You’re limited to claiming a hex / month and you don’t really have the resources for much more than that anyways. So if you do the math, 12 months is basically just enough for covering the territory between Oleg’s and the Castle.